None of the above. Unless you're already running a $1000+ monitor setup, you're wasting lots of money that can better be spent (for a gamer) on things like monitors, etc.
P.S. For rendering, the programs you use more often may have a heavy affect on which GPU brand (AMD for the 7970, Nvidia for the 680) will be better for you. I'd check program-specific forums for those programs that are most imortant to you.

I totally agree with this, don't go with two GPU's unless you have atleast 3 monitors. Complete waste.

Either SSD would be good, I personally just like to have the lastest and greatest when I buy new things, and the 840 is cheaper than the M4 in the US, which is why I normally just put it in my builds.
The Crucial M4, Plexor M5, Samsung 830 are all great alternatives to the Samsung 840. There wont really be any noticeable difference in speeds either.

point of interest, what is the difference between 840 and 840 pro, and is Vertex4 or Neutron GTX competitors to these drives too?